Heating metal bodies preparatory to hot working



,f Aug. 27, 1946. K. MARSH HEATING METAL BODIES PREPARATORY TO HOTWORKING'l Filed nec'. '28, 194s #ww/@91M ATTORNEY Patented Aug. 27, 1946HEATING METAL BODIES PREPARATORY TO HOT WORKING Kirtland Marsh,Pittsburgh, Pa., assignor to Aluminum Company of America, Pittsburgh,Pa., a corporation of Pennsylvania Application December 28, 1943, SerialNo. 515,938

.This invention relates to a process for heat conditioning metal bodiesof considerable mass, particularly ingots, for hot working, and it ishereinafter described in connection with the treatment of ingotspreparatory to hot rolling or breakdown. Y

To sustain a high output schedule, a common practice of processingingots to bring them into the desired metallurgical and thermalconditionsV for hot rolling 'is carried out by the well known "soakingpit procedure. This practice has various known deficiencies anddisadvantages; Among them may be mentioned the individual handling ofeach ingot for removal from the heating or combustion zone, thefluctuation in pit temperature and waste of heat and fuel upon removalof the covers to expose an ingot ywhich it is desired to remove withconsequent deleterious effecten other ingots in the same heat zone orpit but not yet removed, and especiallythe lack of temperatureequilibrium or uniformity in all parts of the ingots when they reach themill for rolling, particularly as between the interior and exteriorportions thereof.

Itis among the objectives of this invention to provide a process whichovercomes the foregoingand other difficulties, which eliminatesindividual` handling of the ingots being processed, which results inmaximum economy in the employment of heat and maximum conservation ofheat, and by which treated or processed ingots of more uniform thermaland metallurgical conditions are produced for hot working under suchpredetermined schedule as may be desired and atpmaterially lower costs.A further object of the invention is to provide an improved processwhereby a large number or multiplicity of ingots may be heated up to andheld at a predetermined preheating and soaking temperature above theworking temperature to condition the same metallurgically, andthereafter rapidly vbringing the ingots to hot working or rollingtemperature, effectively establishing temperature equilibrium,throughout each ingot in readiness for rolling, and holding themindefinitely in ready condition for delivery to the mill one by one asneeded. Other objects and advantages will become apparent from thefollowing description of the invention.

By way of example, the accompanying draw- 6 Claims. (Cl. 26S-52)inglshows diagrammatically certain apparatus mally treated, and Fig.r 2illustrating a second y furnace equipment in. which a redistributedbatch of ingots is further processed.

The nature of the preferred embodiment of the present invention may bedescribed in general terms as including the steps of forming a multiplelayer, stack or pile of the bodies or ingots to be treated with aplurality of ingots in each layer or row, introducing one or more of thepiles into a soaking-preheating chamber held at a predeterminedtemperature above working temperature, subsequently` removing a pile o-fheated ingots from said chamber, transferring all the ingots in thepile, in layers or in units, successively to a second furnace, andintroducing the said layers of ingots into said second furnace,utilizing residual heat in the ngots while they are in the secondfurnace to cause equalization of temperature throughout each ingotrapidly, and advancing the ingots through the second furnaceintermittently to effect discharge thereof for delivery to the mill asneeded. The temperatures employed in each of the respective furnacechambers will depend upon the characteristics of the metal beingtreated, and specie.` temperatures need not be here mentioned as theyare well known to the metallurgist, and for-a given kind of metal theusual temperatures required to effect the desired results will beutilized. Some bodies of alloyed metals prior to initial hot workingthereof require heating to a temperature above hot working temperatureand soaking at that elevated temperaturefor a substantial length of timeto improve the metallurgical characteristics, in addition to renderingthe metal readily workable. Among the charf acteristicsY so improved byheating and soaking isl that of structural uniformity, i. e.,the'heating causes some diffusion of alloy ingredients in the base metalwith consequent "diminution in size of brittle constituents thatinterfere with properA Working of the bodies. will bev particularlyadvantageous for thevtreatment of metal bodies or ingots of such metal,aluminum alloys being a particular example.

` In one mode of practicing the invention, and withreference tothedrawing, a horizontal furnace 8 is provided, into the heating chamber ofwhich the ingots are charged and there heated up to and held at adesired high temperature. The construction of this furnace may take anywell known form. Preferably, it will have a heat, ing chamber 9, spacedfrom the walls of the furnace-and adapted forforced circulation of thefurnace atmosphere by means of `suitable` cir- The invention p Vof eachingot and the average or mean temperature of al1 the ingots are causedto be brought into a greater degree of uniformity, which manifestsitself in the working operation subsequently performed. In theprocessing of metal bodies or ingots of certain kinds of metal, it maybe advantageous to provide a non-oxidizing or inert atmosphere in theholding furnace I5 if desired.

It is preferred to discharge all of the ingots from the holding furnaceI5 before introducing another batch thereinto, so that temperatureconditions therein can be more readily maintained uniform andfluctuations and heat losses kept to a minimum, and crosswise ingotdisposition enables a furnace and its conveyor mechanism of greatlysimplied construction to be employed, Accordingly, it is preferred toprovide at least an additional holding furnace 25, in all respects aduplicate of the furnace I5, arranged to'discharge its ingots to therunway or roller table 22, so that uninterrupted iiow of ingots to themill can be accomplished. This furnace 25 will be charged with an entirepile or batch of ingots from the soaking-preheating furnace 8 while themill is being supplied with ingots from the furnace I5. After the supplyof ingots is exhausted from furnace I5 delivery of fully processedingots from the furnace 25 is effected. A suiiicient number of furnaces8 will be used to supply batches of ingots to the holding furnaces I5and 25, alternately, to meet the predetermined schedule or requirementof the mill. The discharge of ingots from the respective holdingfurnaces may be under control of the mill operator. Since each of theingots as discharged from one of the holding furnaces is in requiredrolling condition thermally and discharge thereof is effected only asneeded at the mill, there is eliminated by this invention thatinterdependency between the operation of themill and the operation ofassociated pits extant in prior practices.

What is claimed is:

1. A process for heat conditioning cast metal bodies of an aluminumalloy and the like for initial working at a given hot workingtemperature comprising introducingv simultaneously into a heatingfurnace a multiplicity of said bodies removing said bodies from saidfurnace simulltaneously after bringing them to and maintaining them at atemperature greater than said working temperature to effectmetallurgical oonditioning thereof, cooling said removed bodies in air,introducing all of said removed bodies into a second furnace in side byside relation at an average temperature about equal to said workingtemperature to check cooling thereof, effecting equalization of thetemperature of said bodies in said second furnace at substantially saidworking temperature, and moving said bodies through said second furnaceto discharge them one at a time.

2. The method of treating cast metal alloy bodies preparatory to initialhot working at a given hot working'temperature whichcomprises,introducing a .batch of said bodies intoL a furnace heated to atemperature above said working` 17em-` perature, heating and soakingsaid bodies in said f.urnace,'withdrawing the batchv of heated bodiesfrom said furnace, charging all'A the bodies constituting said batch inspaced relationship intoLa second furnace normally maintainedsubstantially at said working temperature, for subsequentv dischargetherefrom'oneat atime, as needed for working, allthe bodiesinsaid-second furnace being held substantially at said working temperatureuntil discharged therefrom, and imparting intermittent movement to thesaid bodies in said second furnace to discharge one of them.

3. The method of treating cast metal alloy bodies preparatory to initialhot working at a given hot working temperature which comprises,introducing a batch of said bodies into a furnace heated to atemperature above said working temperature, heating and soaking saidbodies in said furnace, withdrawing the batch of heated bodies from saidfurnace, charging all the bodies `constituting said batch in spacedrelationship into a second furnace normally maintained substantially atsaid working temperature, for subsequent discharge therefrom one at atime, as needed for working, all the bodies in said second furnace beingheld substantially at said Working temperature until dischargedtherefrom, imparting intermittent movement to the said bodies in saidsecond furnace to discharge one of them, similarly charging all theheated bodies of another batch into a third furnace identical to saidsecondfurnace during discharge of bodies from the latter, and effectingdischarge of bodies from said third furnace after al1 the bodies havebeen discharged from said second furnace.

4. The method of preparing cast metal alloy bodies for initial workingat a given hot Working temperature which comprises, introducing a loadconsisting of a multiplicity of said bodies arranged in spaced piledrelation into a furnace, heating said load to and soaking the same at atemperature higher than said working temperature to effect metallurgicalconditioning thereof, removing the load after soaking is completed,effecting rearrangement of the said bodies of said load and introductionthereof into a second furnace without reducing the mean temperature ofsaid bodies materially below said working temperature, equalizing thetemperature of said bodies in said second furnace, prior to dischargefrom said second furnace, and imparting intermittent movement to saidbodies in said second furnace to discharge them only as needed forWorking.

5. The method of preparing cast metal alloy bodies for initial workingat a given hot working temperature which comprises, introducing a loadconsisting of a multiplicity of said bodies arranged in spaced piledrelation into a furnace,

heating said load to and soaking the same at a temperature higher thansaid working temperature to effect metallurgical conditioning thereof,removing the load after soaking is completed, effecting rearrangement ofsaid bodies of said load and introduction thereof into a second furnacewithout reducing the mean temperature of said bodies materially belowsaid working temperature, equalizing the temperature of said bodies insaid second furnace primarily by the residual heat in each of them,prior to discharge from said second furnace, and imparting intermitteilt`novement tojsaid .bodies Lin said second l furnaoe ftov :discharge'them only as :needed Afor' working` 6. process :for `heatoondti'oningiingots cony8 perature to Yeiect metallurgical conditioningthereof, ivremoving Lthe .pi-'1e :of lingots .from .said furnace aftersoaking is completed, removing the layers voi'the fpil'e 1inAsuccession, and introducing themrnto *a second iurnace in asingle'rlayeriin spaced irela'tionship, maintaining ysaidiingots .in f

said second .furnace `at 4a. temperature substan tialiy equal tozsaidrworking temperature, and' Y moving said ingots through said secondfurnace 1-0k to disohancge :them one ata time.

